Fluid cooling of reciprocating pistons



2 Sheets-Sheet 1 [NYENTOR ATTOENEY S E. E. CHATTERTON FLUID comm; 0F RECIPROCATING PISTONS t 7 m 91a E F-t United States Patent FLUID COOLING OF RECHROCATING PISTONS Ernest Edward Chatterton, London, England, assignor to D. Napier & Son Limited, London, England, a company of Great Britain Application November 8, 1954, Serial No. 467,613

Claims priority, application Great Britain November 9, 1953 3 Claims. (Cl. 12341.38)

This invention relates to pistons for internal combustion engines and of the kind comprising a crown portion and a skirt portion with a ring-carrying portion between them provided with one or more ring grooves, and more particularly to pistons for internal combustion engines designed to operate under high load or other conditions in which the rate of heat flow to the piston tends to be high.

It has already been proposed in the present applicants British Patent No. 649,351 to provide a piston which is cooled in the neighbourhood of the ring grooves by the action of a cooling liquid which under the reciprocating action of the piston is shaken from one end to the other of an annular cooling chamber formed in the part of the piston around which the grooves lie and extending towards or into the skirt portion of the piston, and at the same time to provide a separate cooling circuit for the flow of cooling liquid through a crown-cooling chamber situated immediately beneath the piston crown.

The present invention is concerned with an improved arrangement of piston of the kind referred to tending to provide an increased transfer of heat to the cooling liquid and to prevent carbonisation of the cooling liquid and possible blockage of the cooling liquid passages due to carbonisation of the cooling liquid at high temperature points.

For convenience it will be assumed herein that the piston is vertical with its crown at its upper end, but it is to be understood that the invention is equally applicable to pistons having their axes horizontal or inclined as well as to pistons arranged with their crowns at their lower ends in cases where the speed of reciprocation of the piston during normal operation is such that the effect of momentum on the cool liquid outweighs gravitational effects.

According to the present invention a piston of the general kind referred to has an annular cooling oil chamber behind the ring groove or grooves extending towards or into the skirt portion and closed at its lower end, a crown cooling chamber extending across the under face of the crown from adjacent to its centre to adjacent to its circumference where it communicates with the adjacent upper end of the annular chamber, a series of loop passages leading from points intermediate in the length of the annular chamber to approximately the centre of the crown cooling chamber, means for admitting oil to the annular chamber and one or more oil outlets for the ejection of surplus oil from the annular chamber leading from the annular chamber at a point or points intermediate in its length, the arrangement being such that cooling oil thrown to the upper end of the annular chamber during the last half of each upstroke of the piston will tend to pass the lower ends of the loop passages and thus be forced by its momentum when it reaches the upper end of the annular chamber into and inwards through the crown cooling chamber into the upper ends of the loop passages whereby during the last half of the downstroke of the piston this oil will tend to be returned to 2,788,774 Patented Apr. 16, 1957 the annular chamber downwards through the loop passages.

The arrangement will preferably be such that the volumetric capacity of the part of the annular chamber which lies either above or below the oil outlet or outlets 'is smaller than the combined volumetric capacities of the crown cooling chamber and that part of the annular chamber which lies above the lower ends of the loop passages, so that the volume of oil retained in the annular chamber will be such that at the end of each upstroke of the piston the whole volume of oil in the annular chamber will tend to be thrown past the lower ends of the loop passages.

Moreover since the passage of oil from the upper end of the annular chamber into the crown cooling chamber at the moment when the oil reaches the upper end of the annular chamber may be somewhat delayed by the sudden change of direction, it may be preferable to make the volumetric capacity of the part of the annular chamher which lies either above or below the oil outlet or outlets not greater than the volumetric capacity of'the part of the annular chamber which lies above the lower ends of the loop passages so that the whole volume of oil retained within the annular chamber can be accommodated in the part of this annular chamber above the lower ends of the loop passages.

In this connection it will be appreciated that during reciprocation of the piston each time the oil is thrown to that end of the annular chamber which has the lesser volumetric capacity measured from the transverse plane in which the outlet or outlets lie, surplus oil will tend to be ejected from the outlets, and that the quantity of oil maintained in the annular chamber during operation will tend to be approximately that which will just not cover these outlets when all the oil is thrown to such end of the chamber.

The details of construction may vary considerably but one construction of piston according to the invention is shown by way of example in the accompanying drawings, in which Figure 1 is a sectional side elevation of the piston and the upper end of its associated connecting rod in a plane at right angles to the axis of the gudgeon pin,

Figure 2 is a sectional elevation of the piston partly in each of two planes, that is on the line 2-2 of Figure 3, and

Figure 3 is a cross-section on the line 33 of Figure 2. I

In the construction illustrated the piston comprises two main parts, namely an outer part comprising a crown A and a ring-carrying portion A by which the crown is connected to the skirt portion A and an inner part B which fits closely within the outer part after the general manner of a plug and includes the usual gudgeon pin bosses B near its lower ends. The inner part B is retained within the outer part by means of a tapered circlip C engaging a groove in the skirt portion A2 of the outer part as shown, and bearing through a thrust ring D on the lower end of the inner part B.

The inner circumferential surface of the outer part A A and the under surface of the crown A, and the outer circumferential surface and the upper surface of the inner part B are formed so that they co-operate to provide an annular oil cooling chamber comprising an upper part B lying behind the ring-carrying portion A and a lower part B which extends downwards into the skirt portion A to a point just below the gudgeon pin P which is supported in the .gudgeon pin bosses B the part B of the annular cooling oil chamber communicating at its upper end with a crown cooling oil chamber comprising a series of radial passages G the inner ends of whichcommunicate withapocket G while theirouter ends communicate with the upper end of the annular cooling oil chamber E, E

As shown in Figure-1',-the connecting-rod H includes an oil delivery passage H through which in known manner, oil is fed from the crankshaft, this oil deliverypassage, in addition to feeding oil to the gudgeon pin bearing H being arranged to deliver oil through an annular passage H to a port H which communicates with an oil receiving chamber J formed partly by a recess in therinner portion 'B'of' the piston and partlyby a cylindrical surface on the gudgeon pin which makes a substantially oil-tight 1 seal with corresponding surfaces at the edges of the recess J, V a r Formed in theiinner. part B of the piston. are two oil inlet passages J the inner ends of' which communicate with the chambersl while theirtoutert ends communicate ber E, E into the interiortof the innerpa'rt B of the piston and thence out through the lower end ofthe piston.

Extending between the pocket'G andrthe .annular.

" cooling oil chamberrE, E aretwo loop'passag'e's each comprising an outwardly inclined section il 'leading from and escape of oil from the annular chambertE, E v in the way mentioned, a circulation of oil round the circuit comprised by the upper part E of the annular chamber,

the'crown cooling chamber G, G and the loop passages 1 ,5 It will be appreciated that the quantity of oil maintained within thetpiston as a whole will tend to be controlled and maintained constant by reason of" the position of the outlet ports J which ensures'thatonly 7 1'1. A piston of the kind referred to having-an annular chamber behind the ring grooves extending'towards the shirt portion and closed at itslower end, having an outer wall formed by the inner surface'of' the'outer wall of the piston and an inner wall formed by an inner plug; a

crown cooling chamberfclosely' extending. across the under face; of thetcrown fromadjacent toiits center to adjacent to' its circumferencerwhere; the crown cooling chamber communicates with: the adjacent upper end of the annular chamber, aseries'iof loop. passages formed in the pocket G and a substantially radial section J. leading a from the lower end of the portion J into the, annular cooling oil chamber E, E

As shown the mean diameter of the lower'endpor tion E of the annular cooling oil chamber as; well as" its cross-sectional area are greater than the correspond- 7 ing dimensions of the upper portionE, and the form of the.

parts is such that-the change of direction of the oil fiow' at the junction ofth e upper and lower portions E, E} as. the oil is thrown from the lower portion E to the upper I portion E towards the end of each upstroke of the piston will be completed before the oilreaches the lower ends.

J 'of the loop fpassages I I so that, when-the oil is thrown upwards it will tend to be thrown past the ends the upper end of the; annular chamber into andiinwards' :tlirough'the crown cooling chamber into the upper ends of the loop passages, whereby duringthelasthalfof the down-stroke of the pistontthis oil will tend tobe returned to the annular chamber downwards througl'rthe of the passages-I into the upper end of the portionE of the annular chamberand thusinto the crowncooling chamber G, G whence it will tend to flow to the appropriate level down the loop passages 1 When during the following downstroke of the; piston" the oil then tends-to be thrown to the lower end of-the annular chamber EyE the. part of the oil still; in

t the upper portion of'tthischamber, will tend to be I thrown directly downwards, since air from the lower end of theannular chamber can morereadily reachthis point than any point in crown cooling chamber- G,

G while the oil in the upper ends of the loop passages l' J is thrown down'through the loop passages into'the annular chamber E, E and tendstto draw with it the oil in the crown cooling chamber G, G

It will be appreciated that during reciprocation of the ing chamber communicates with the annular chamber-to approximately the center ofithe crown cooling chamber,

means for admitting oil to the, annular chambentand at least'one oil outlet-for the ejection of surplus oil from;

the piston formed in the innerwall of the annular chamchamber during the last half ofeach upstroke'ofcthe piston will tendtto pass the lower ends of the loop passages and be forced by its momentumjwhen it reaches I loop passages. I

piston oil will be delivered through the port H chamthere will be superimposed upon the delivery of oil to 2. A piston of the kind ref erred to as claimed in claim 1, in which the' yolume tric capacity ofthe part' of the chamberlying below the. oil outlets issubstantially smaller than the combined volumetric. capacities of the crown, chamber andthat part of the an 7 Vnular chamber whichlies above the lower ends of the loop passages.

{,3. A piston or thekind referred to as claimed in claim 1;. in whichthe volumetric capacity'of the part of the annular chamber which lies to the side of the oil outlet ofoutlets nearert one endrof the annular chamber is not greatertthan'the volumetric capacity of thepart of the.

annular chamber which liesabove the lower ends ofthe loop'passage or passages.

References Cited' in the file'of this patent "UNITED 1 STATES PATENTS? 

